There are 2 probable causes:
1 - Broken key caps. Those are the parts you actualy push.
Symptoms: You may be able to have the key work by pressing hadrer. The key could get stuck or don't move smoothly.
Removing the key cap allow access to the actual switch that you may be able to activate with a finger of a crayon.
You may be able to get a replacement. It may cost you only a few cents, or be free if you can salvage one from another similar keyboard.
2 - The actual switch is worn out.
Symptoms: The key moves smoothly. There may have been a period when you could use the key by pressing harder, but it no longer works, or the keys may had a period of erratic functionning.
Prognostic: BAD!
Several other keys are surely about to also malfunction.
Cure: Get and install a new keyboard as it's not possible to replace a single key switch.
Look at your local computer shops or look on eBay or any other online shoping resources.
Electro, June 2012
